A technique has been developed in recent years for obtaining cast strips with a thickness of 10 mm or less by direct casting from molten steel, and actual apparatuses therefor have been tested. With the new technique, it is possible to simplify or even eliminate the hot rolling process.
Conventionally, slabs with thicknesses of over 100 mm have required hot rolling with a hot rolling mill involving a large consumption of energy, and thus the advantages of simplifying or eliminating the hot rolling step include not only lowering of production costs, but also benefits from the standpoint of the environment. Hereunder, the process including the step of casting a thin strip with a thickness of 10 mm or less from molten steel will be referred to as the "new process", and the process including hot rolling a slab into a hot-rolled strip will be referred to as the "existing hot rolling process".
Conventionally, when Cr--Ni-based stainless steel hot-rolled annealed sheets, typically 18% Cr-8% Ni steel, are produced by the existing hot rolling process, a hot rolling reduction of about 98% or greater results in development of a strong hot rolling texture, and after annealing of the hot-rolled sheet the (100)[001] texture develops.
By casting of thin cast strips without the hot rolling step in the new process, it is possible to prevent formation of the (100)[001] texture which is a characteristic of hot-rolled annealed sheets, and thus produce a steel strip with low anisotropy. However, the resulting thin cast strip strongly develops a (100)[0vw] texture which is a characteristic of solidified structures.
Attempts have also been made to hot roll cast strips using the new process. For example, in Japanese Patent Application No. 61-141433, a Cr--Ni-based stainless steel cast strip is subjected to hot rolling at 800.degree. C. or higher to a reduction of 50% or less followed by cold rolling to produce a thin sheet product, by which it is possible to produce a thin sheet with excellent surface quality; however, the anisotropy of such hot-rolled steel sheets had not been studied.